Generally, an image reading apparatus such as a scanner apparatus, copier or the like is configured of a platen, a light source for irradiating reading light on a reading surface on the platen, reflecting mirrors for reflecting light reflected from the reading surface to predetermined directions, a condenser lens for forming an image by light from the mirrors, and a sensor for photoelectric conversion for converting light from the lens through the condenser lens into electricity.
For example, Japanese Laid-Open Patent Publication (Kokai) No. 2005-234297 (Patent Document 1) discloses an image reading apparatus comprised of a reading mechanism with a reducing optical system. This document discloses an image reading apparatus in which, in a carriage reciprocating along a platen, there are provided a light source lamp, a plurality of mirrors for reflecting light reflected from a reading surface to predetermined directions, and a sensor for photoelectric conversion for converting light from the mirrors through a condenser lens into electricity.
In such an image reading apparatus, light is irradiated from the light source lamp to the reading surface at a predetermined angle direction, and diffusion light from the reading surface is reflected by the reflecting mirrors to a reading light path direction. That is, since the reading surface of an original document is not a complete plane but is a fine concave-convex surface (for example, roughness of the surface of a paper), linear light having a predetermined width is irradiated to read an image by light directing to the mirror surface of the mirror (diffusion light). In this case, when an image (for example a gilt character) is formed on an image surface having a smoothly-shaped gloss surface, there is a phenomenon where light from the light source lamp does not direct to the regular reflection direction and does not enter into the reflecting mirrors. Due to this, it is known that the gloss image is read as black.
Accordingly, in Japanese Patent Gazette No. 4083042 (Patent Document 2), for example, there is proposed to provide a diffusion light source for irradiating light from a predetermined angle to a reading surface, and a regular reflection light source for irradiating light from directly below the reading surface; and from an original document including a gloss image, read data is obtained by synthesizing read data obtained by irradiating light from the diffusion light source and read data obtained by irradiating light from the regular reflection light source.
In this document 2, there is proposed a mechanism in which light sources are arranged in two directions where light from a first light source is irradiated in a direction inclined by a predetermined angle (θ1) with respect to a reading light directing from the reading surface to a reflecting mirror, and similarly light from a second light source is irradiated in the direction inclined by an angle θ2. Then, the angles are set as θ1>θ2 so as to guide the reflected light of diffusion light from the first light source to the reflecting mirror. To this end, it is most preferable to arrange the second light source in a light path incident on the reflecting mirror.
However, since it is impossible to arrange the second light source in the light path incident on the reflecting mirror (θ2=0 degree), in the apparatus disclosed in the document 2, the second light source is arranged at a position close to the light path with a degree in which the second light source does not block the light path incident from the reading surface on the reflecting mirror. In such an arrangement of the structure, in order to get closer the incident angle (θ2) irradiated from the second light source to the reading surface to be 0 degree, the light path length from the light source to the reading surface must be kept long. Therefore, a problem has been known in which the apparatus becomes large.
Further, in Japanese Laid Open Patent Publication (Kokai) No. 2000-123152 (Patent Document 3), there is proposed to configure a reflecting mirror by a half mirror, and to arrange a second light source at the back surface side of the reflecting mirror arranged directly below a reading surface.
Note that Japanese Laid Open Patent Publication (Kokai) No. H11-317854 (Patent Document 4) discloses an image reading apparatus utilizing a fluorescent light as a light source, wherein a flat glass is arranged on an opening portion of a glass tube which construct the fluorescent light; a reflection film is provided on a part of an outer surface of the flat glass; a light flux is emitted from a part, on which a reflecting film of the flat glass is not provided, to irradiate an original document; and light flux from the original document is reflected from a part on which the reflecting film of the flat glass is provided. In this document 4, a problem is to higher the lighting efficiency of the fluorescent light which has a low brightness and large light emitting area, so as to downsizing the apparatus, and there is no disclosure about an apparatus in which light is irradiated from two different directions to a reading surface of an image.